Partner Magazine logo 15

logo 39 • the CAMLOG Partner Magazine • November 2016 23 optical profilometry (focus variation microscopy), we examined the micro- design below the shoulder of CAD/CAM abutments of various manufacturers in a study. The objective was to define the ideal topography and surface roughness respectively. Today, we can presume that there is a threshold value at which bacterial and plaque accumulation on the surface is low while at the same time promoting the accumulation of fibroblasts (Fig. 5) . If the surface is too rough, this bears the risk of increased plaque accumulation. However, if the surface is too smooth, the fibroblasts of the peri-implant mucosa cannot "attach" optimally. Therefore a medium roughness value (in μm: Ra = 0.21-0.40) is regarded as the ideal surface. During the investigation on CAD/CAM fabricated abutments, a ten-fold higher surface roughness was detected in parts. In other words, this requires reworking to achieve the mean roughness value. According to our validated processing protocol (see surface cleanliness), the CAD/CAM hybrid abutments offer optimal roughness and demonstrate good conditions for the desired accumulation of peri-implant tissue. Consequence for lab and practice routines In order to generate perfect surface finishing for all prosthetic implant abutments, we have defined a documented, validated work protocol. According to this protocol we machine the basal region of the abutment with special diamonded rubber polishers (Serius Ceramics, Frankfurt/Main) and so obtain a surface of between 2 to 4 microns of residual roughness, the proven standard for optimal tissue accumulation (Fig. 6) . Surface cleanliness It has been proven that contamination can occur on implant abutments – regardless of being customized or pre-assembled – which leads to questions regarding a long-term stable outcome (Fig. 7) . The following applies as a matter of principle: customized abutments are medical devices which are classified as being semi-critical (Robert-Koch-Institute, RKI). In other words, professional cleaning must be CASE STUDY Fig. 5: The traffic light system for the classification of roughness in the basal region could be established as follows [1]: Rough = > 0.41 μm (red: increased risk of plaque accumulation) Smooth = < 0.2 μm (amber: reduced accumulation of fibroblasts) Medium rough = 0.21 – 0.4 μm (green: perfect) Fig. 6: Reworking of the surface in the basal, submucosal region with special rubber polishers. The desired residual roughness of 0.2-0.4 μm was achieved. Fig. 7: The three images in the top row show contaminated components. The bottom three images show the same surface after applying the validated cleaning process presented here.